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[24.132.120.189]) by smtp.gmail.com with ESMTPSA id y5sm7617545wrd.75.2021.10.25.15.16.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 Oct 2021 15:16:54 -0700 (PDT) Received: from avar by gmgdl with local (Exim 4.95) (envelope-from ) id 1mf8H0-001gZ5-6l; Tue, 26 Oct 2021 00:16:54 +0200 From: =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason To: Han-Wen Nienhuys Cc: Johannes Schindelin , git@vger.kernel.org, Philip Oakley Subject: Re: [Summit topic] The state of getting a reftable backend working in git.git Date: Tue, 26 Oct 2021 00:09:55 +0200 References: User-agent: Debian GNU/Linux bookworm/sid; Emacs 27.1; mu4e 1.6.6 In-reply-to: Message-ID: <211026.86wnm021ih.gmgdl@evledraar.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Mon, Oct 25 2021, Han-Wen Nienhuys wrote: > On Thu, Oct 21, 2021 at 1:56 PM Johannes Schindelin > wrote: >> >> This session was led by =C3=86var Arnfj=C3=B6r=C3=B0 Bjarmason (on behal= f of Han-Wen >> Nienhuys, the driving force behind the reftable patches, who did not >> attend the Summit). Supporting cast: Jonathan "jrnieder" Nieder, Johannes >> "Dscho" Schindelin, Philip Oakley, Jeff "Peff" King, and Junio Hamano. >> > > Thanks =C3=86var for doing this. I wanted to be there, but I took a much > needed 2 week computer-less vacation . No problem, as is perhaps clear from the notes I had to hand-wave some questions away since I didn't know about those things. >>.. >> 9. Reftable has a set of files that go together. May want debuggin= g tool >> to dump the content of a binary reftable file. But we can >> incrementally add those > > > The patch series includes a test-tool for dumping both individual > tables and a stack of tables. It's not super-polished, but it gets the > job done. > > $ touch a ; ~/vc/git/git add a; ~/vc/git/git commit -mx > ... > > $ ~/vc/git/bin-wrappers/test-tool dump-reftable -t > .git/reftable/0x000000000002-0x000000000002-327b23c6.ref > ref{refs/heads/main(2) val 1 ab21c324503544acca84eb55f5ee7dce24b23e15} > log{HEAD(2) Han-Wen Nienhuys 1635188263 0200 > 0000000000000000000000000000000000000000 =3D> > ab21c324503544acca84eb55f5ee7dce24b23e15 > > commit (initial): x > > } > log{refs/heads/main(2) Han-Wen Nienhuys 1635188263 02= 00 > 0000000000000000000000000000000000000000 =3D> > ab21c324503544acca84eb55f5ee7dce24b23e15 > > commit (initial): x > > } Neat. >From memory I think the more general concern Philip Oakley was also expressing (but maybe he'll chime in) could also be addressed by a tool that just un-reftable-ifies a repository. I think such a thing would be useful, and I think we don't have that already. Isn't the files backend or reftable usage now an "init"-time setting. It would be useful if for no other reason than to give user who are looking at a repository that's weird somehow the ability to quickly migrate 100% away from reftable, to see if it has any impact on whatever they're seeing. I wanted to implement a "git unpack-refs" a while ago for "pack-refs", just to simulate some performance aspects of loose-refs without writing an ad-hoc "ref exploder" one-liner again. A migration tool would surely be pretty much that, no? I.e. we'd just create a .git/refs.migrate or whatever, then hold a lock on reftable, and in-place move .git/refs{.migrate,} (along with top-level files like HEAD et al, presumably...). Maybe there's more complexity I'm not considering than just the *.lock dance in .git/*, but if not such a tool could also convert freely between the two backends, so you could try refable out in an existing checkout.